The U67 in Depth

One of the evergreen classics in the world of microphones is the Neumann U67. It is a multi-pattern tube condenser microphone which was presented to the world in 1960. It was the successor to the legendary Neumann U47—although they did exist in parallel for a few years. Over the years and decades it has become one of the most sought-after vintage microphones out there. It's time to shine the spotlight on the U67 in depth. Here’s the history of why it came about, how it was designed and what variants and versions there have been.

To get you started, watch this brief video introduction for the two 67 models included with Sphere:

U67 Uses

The U67 was designed with versatility in mind. And indeed—you would be hard pressed to find a sound source where it doesn’t work. Its detailed but smooth midrange makes it a top choice for close-miked vocals, pianos (it was reportedly picked for the piano part in The Beatles’ A Day in the Life), guitar amps, acoustic guitars, drum overheads and horns.

In a recent video shot at Capitol Studios in Los Angeles, legendary engineer Al Schmitt uses U67s set to omni on the saxophone players in a big band recording. He comments that any leakage from the other instruments doesn’t bother him, as even the leakage sounds good with U67s! Catherine Marks of Assault & Battery 2 in London on the other hand swears by 67s for electric guitars with lots of top-end sparkle.

So basically, the U67 is a safe bet. It will rarely be the wrong choice, and in many cases, you’ll find that it is the very best choice.

History

Towards the end of the 1950s, several things led to Neumann starting on the design of what would become the U67. Perhaps most importantly, the recording technique of placing microphones close to their sources had become very popular during the 50s. While this technique has great advantages, it poses some challenges on the mic design. Neumann therefore saw a market gap for a microphone that was designed with close placement in mind. Furthermore, Neumann wanted to make their new microphone truly versatile. One aspect to fulfill this goal was to introduce a large diaphragm condenser offering a figure-of-eight pattern in addition to omni and cardioid. At the time, Neumann had already experienced success with their KM56 small diaphragm condenser, which offered three switchable polar patterns. Furthermore, Telefunken had announced that they would cease production of the VF14 tube. That tube was a vital component in Neumann’s then flagship model U47, so it was clear Neumann needed to start designing the successor.

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Design Details

High-pass

One thing we all love about close miking with a cardioid pattern microphone is how the proximity effect typically adds a robust bottom end to the sound. But the low-end can also easily get overbearing. This was one of the problems Neumann addressed with the U67. The microphone’s amplification circuit was designed with a permanent low-frequency roll-off, to reduce frequencies below 40 Hertz, with the purpose of reducing mechanical noise and avoiding the risk of having the low frequencies overloading the amp circuit. The filter could be bypassed by opening the microphone and disconnecting a wire bridge. But to further control the low end when using close mic techniques, a switch on the microphone body let the user easily switch the low-cut filter’s frequency to 100 Hz—although the graphs in the original U67 brochure actually showed that the roll-off started as high as 200 Hz.

Pad Switch

One other problem with close mic techniques is that the microphone is exposed to much louder sound levels than when the mic is placed at a distance from the sound source. So there’s a risk of overloading the microphone’s amplifier, not only with low frequencies, but across the entire frequency spectrum. Therefore, a switchable attenuator was added to alter what the U67 owner’s manual referred to as the “transmission ratio”, the sound level that was fed into the amplifier circuit. The attenuator—the “pad” as it’s commonly called today—reduced the overall amplitude by 14 decibels. Townsend Labs’ measurements show that the attenuation is actually not perfectly linear. Engaging the pad gives a slight extra roll-off of the low and high frequencies. Consequently, we’ve made this setting available in the “Filter” section of the plug-in.

The Sphere plug-in GUI gives access to all the parameters of the original 67s, including polar patterns and unique filter settings.

For added versatility, it was also important that the microphone had an improved signal to noise ratio compared to previous microphones. So several innovative design solutions were applied to fulfill this request. The sibilant frequencies around 6 kHz were also attenuated by design, as sharp “s” and “t” sounds are yet another downside of close mic placement to a vocalist.

When the U67 was released in 1960, it was an enormous success. Such a success that a few years into the microphone’s existence, the US distributor made an ad that simply consisted of a photo of the microphone with the words “Ask anyone” below. No logos or anything! The mic’s iconic exterior design with the tapered body and wedged grille had quickly become so well-known and recognizable that the marketers could choose such an understated messaging.

U67 Variants

Neumann also released the M269 for the German broadcast market. It’s basically a U67 with an AC701k tube instead of an EF86. Some would say the end result is a mic that sounds even better than a 67. The M269 also has a multi-pattern switch on the power supply, whereas the U67 only has three patterns which are selectable from the mic body. Interestingly, the M269 also has a switch on the body that provides a dedicated cardioid mode.

In the early 1990s, a collection of new old stock U67 parts from the 1960s were discovered in a warehouse. Neumann decided to assemble a few hundred microphones out of these parts and sell them as U67 SLO Edition—super limited offering.

But regardless of vintage, the U67 sound can vary quite a lot from unit to unit—see the Measurements section below. These differences are largely due to manufacturing tolerances and aging. But different factory parts and minor design changes also play a role.

The 2018 Reissue

Early 2018, Neumann announced a U67 reissue microphone. It was presented as being identical to the vintage ones, but there are a few design differences that can make a discernible difference. Most notably, the capsules are tensioned differently than the vintage U67 which produces a different sonic character.

They all have their strengths and weaknesses. Deciding which one is the best depends on the application and your personal preference. I recently did a quick poll in our Users & Fans group on Facebook to find out which model Sphere owners like the best:

While this may seem like there’s a clear winner, the comments reveal that it’s a bit more complicated than that:

“LD-67 NOS is my favorite for overheads. That extra bit of top is perfect and really brings out the cymbals without adding sizzle. The BP-67 tends to sound pretty special on vocals.” - Matt Hepworth

“BP-67....Drum overheads and some tenor male vocals. I would like to add, I don't dislike any of them. But there's something super silky about the BP that reminds me of a mic I used a long time ago in a Melbourne studio.” - David Pendragon

Why not make up your own opinion and try out the different 67 models available for Sphere? You are invited to install the free, fully-functional native Sphere plug-in. Add our ready-to-go sessions with pre-recorded tracks and you’re ready to take the 67s for a spin:

Measurements & Comparisons

Cardioid

Geek time! Let’s have a look at how the different 67 variants compare and contrast in lab measurements. Here is a plot comparing the on-axis frequency of the three 67s and the 269 in cardioid mode.

As you can see they are all quite different yet have a similar flavor. The 67 I modeled for the LD-67 model has a strong rolloff starting around 6kHz. It can be a great option for a strongly sibilant vocalist or slightly too edgy electric guitars, for example. The other two 67s have a treble bump around 4 to 5 kHz and then also have a nice dip in the sibilant frequencies. Comparing these two, the 67 modeled for the Putnam collection has a stronger low end. Finally, the M269 is kind of like a blend between the other 67s, although it has the strongest bass response of the bunch.

Have a listen to a range of sound examples for all four microphones in cardioid mode:

Omni

Moving on, here are plots comparing the on-axis response when set to the omnidirectional pattern:

Have a listen to a range of sound examples for all four microphones in omni mode:

Figure-of-8

The figure-8 on-axis frequency response is arguably not the greatest and maybe explains why the 67 is not typically used in figure-8 mode:

The on-axis frequency response of microphones really only gives you a small (although not unimportant) idea of the sonic character. Once you start looking at the full 360 degree response, the differences become even bigger. This is because all microphones have a frequency response that is dependent on the direction that sound arrives from. You can read up more on this phenomenon in my The Dark Side of the Mic feature.

All modeled product names are trademarks of their respective owners, which are in no way associated or affiliated with Townsend Labs Inc. These product names and descriptions are provided for the sole purpose of identifying the specific products that were studied during Sphere’s sound model development.

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